/*
 * Copyright (c) MuleSoft, Inc.  All rights reserved.  http://www.mulesoft.com
 * The software in this package is published under the terms of the CPAL v1.0
 * license, a copy of which has been included with this distribution in the
 * LICENSE.txt file.
 */
package org.mule.runtime.config.spring;

import static java.lang.String.format;
import static java.util.Optional.empty;
import static java.util.Optional.of;
import static org.mule.runtime.api.i18n.I18nMessageFactory.createStaticMessage;

import org.mule.runtime.api.dsl.DslResolvingContext;
import org.mule.runtime.api.exception.MuleRuntimeException;
import org.mule.runtime.api.meta.model.ExtensionModel;
import org.mule.runtime.core.api.registry.ServiceRegistry;
import org.mule.runtime.core.registry.SpiServiceRegistry;
import org.mule.runtime.extension.api.dsl.syntax.resources.spi.SchemaResourceFactory;
import org.mule.runtime.extension.api.resources.GeneratedResource;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Optional;
import java.util.Set;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.xml.DelegatingEntityResolver;
import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

/**
 * Custom implementation of resolver for schemas where it will delegate to our custom resolver, then if not found will try to
 * generate the XSDs from the extensions (through {@link SchemaResourceFactory}), and finally fall back to
 * Spring's {@link DelegatingEntityResolver}.
 *
 * @since 4.0
 */
public class ModuleDelegatingEntityResolver implements EntityResolver {

  private static final Logger LOGGER = LoggerFactory.getLogger(ModuleDelegatingEntityResolver.class);

  private Set<ExtensionModel> extensions;
  private final EntityResolver springEntityResolver;
  private final EntityResolver muleEntityResolver;
  private Map<String, String> customSchemaMappings;
  // TODO(fernandezlautaro): MULE-11024 once implemented, extensionSchemaFactory must not be Optional
  private Optional<SchemaResourceFactory> extensionSchemaFactory;
  private Map<String, Boolean> checkedEntities; //It saves already checked entities so that if the resolution already failed once, it will raise and exception and not loop failing over and over again.

  /**
   * Returns an instance of {@link ModuleDelegatingEntityResolver}
   *
   * @param extensions fallback set to dynamically generate schemas from {@link ExtensionModel} if the current {@link #muleEntityResolver} and {@link #springEntityResolver}
   *                             delegates return null when resolving the entity.
   */
  public ModuleDelegatingEntityResolver(Set<ExtensionModel> extensions) {
    ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
    this.muleEntityResolver = new MuleCustomEntityResolver(classLoader);
    this.springEntityResolver = new DelegatingEntityResolver(classLoader);
    this.extensions = extensions;
    this.checkedEntities = new HashMap<>();

    ServiceRegistry spiServiceRegistry = new SpiServiceRegistry();
    // TODO(fernandezlautaro): MULE-11024 until the implementation is moved up to extensions-api, we need to work with Optional to avoid breaking the mule testing framework (cannot add the dependency, as it will imply a circular dependency)
    final Collection<SchemaResourceFactory> schemaResourceFactories =
        spiServiceRegistry.lookupProviders(SchemaResourceFactory.class, getClass().getClassLoader());
    if (schemaResourceFactories.isEmpty()) {
      extensionSchemaFactory = empty();
    } else if (schemaResourceFactories.size() == 1) {
      extensionSchemaFactory = of(schemaResourceFactories.iterator().next());
    } else {
      // TODO(fernandezlautaro): MULE-11024 remove this code once implemented using just spiServiceRegistry.lookupProvider(SchemaResourceFactory.class, getClass().getClassLoader()) (notice the method name chance from  #lookupProviders to #lookupProvider)
      throw new IllegalArgumentException(format("There are '%s' providers for '%s' when there must be 1 or zero.",
                                                schemaResourceFactories.size(), SchemaResourceFactory.class.getName()));
    }
  }

  @Override
  public InputSource resolveEntity(String publicId, String systemId) throws SAXException, IOException {
    if (LOGGER.isDebugEnabled()) {
      LOGGER.debug(format("Looking schema for public identifier(publicId): '%s', system identifier(systemId): '%s'",
                          publicId == null ? "" : publicId,
                          systemId));
    }

    InputSource inputSource;
    inputSource = muleEntityResolver.resolveEntity(publicId, systemId);
    if (inputSource == null) {
      inputSource = generateFromExtensions(publicId, systemId);
    }
    if (inputSource == null) {
      inputSource = springEntityResolver.resolveEntity(publicId, systemId);
    }
    if (inputSource == null) {
      if (checkedEntities.get(systemId) != null) {
        throw new MuleRuntimeException(createStaticMessage("Can't resolve %s %s", publicId == null ? "" : publicId, systemId));
      } else {
        checkedEntities.put(systemId, true);
      }
    }
    return inputSource;
  }

  private InputSource generateFromExtensions(String publicId, String systemId) {
    InputSource inputSource = null;
    // TODO(fernandezlautaro): MULE-11024 once implemented, remove the extensionSchemaFactory.isPresent() from the `if` statement
    if (extensionSchemaFactory.isPresent()) {
      Optional<ExtensionModel> extensionModel = extensions.stream()
          .filter(em -> systemId.equals(em.getXmlDslModel().getSchemaLocation()))
          .findAny();
      if (extensionModel.isPresent()) {
        InputStream schema = getSchemaFromExtension(extensionModel.get());
        inputSource = new InputSource(schema);
        inputSource.setPublicId(publicId);
        inputSource.setSystemId(systemId);
      }
    }
    return inputSource;
  }

  /**
   * Given an {@link ExtensionModel} it will generate the XSD for it.
   *
   * @param extensionModel extension to generate the schema for
   * @return the bytes that represent the schema for the {@code extensionModel}
   */
  private InputStream getSchemaFromExtension(ExtensionModel extensionModel) {
    Optional<GeneratedResource> generatedResource =
        extensionSchemaFactory.get().generateResource(extensionModel,
                                                      DslResolvingContext.getDefault(extensions));
    if (!generatedResource.isPresent()) {
      throw new IllegalStateException(format("There were no schema generators available when trying to work with the extension '%s'",
                                             extensionModel.getName()));
    }
    return new ByteArrayInputStream(generatedResource.get().getContent());
  }
}
